Fix lint in HackfmtFormatter.hack

[alexeyt]

Our CI was failing with:

  + hhvm vendor/hhvm/hhast/bin/hhast-lint
  You have made a lambda which forwards all its arguments to a static method or function.
  The order of the parameters is the same as the order of the arguments.
  You could create a function reference instead. -> \escapeshellarg<>
    Linter: DontCreateForwardingLambdas
    Location: /home/runner/work/hack-codegen/hack-codegen/src/HackfmtFormatter.hack:74:6
    Code:
    >      $option ==> \escapeshellarg($option)

on HHVM latest. Apply the change suggested by the linter.